Translator

ABSTRACT

A transformer for transferring electrical power from a stationary member to a rotating member, with a primary winding and a secondary winding, by means of annular primary and secondary windings disposed in annular slots. The transformer of the kind initially specified can be designed with smaller dimensions and can transfer more power with the same dimensions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a transformer for transferringelectrical power from a stationary member to a rotating member, andcomprising a primary winding and a secondary winding.

2. Description of the Related Art

Such transformers are known as asynchronous machines, in which thestator winding forms the primary winding and the rotor winding forms thesecondary winding, or vice versa. The dissipation heat produced duringpower transfer as a result of hysteresis losses is so considerable that,on the one hand, the transferable power is limited to a few kilowatts.On the other hand, said heat must be dissipated and thereforenecessitates a certain minimum size of transformer with a sufficientlylarge surface.

An alternating-current transformer for brushless transfer, withoutslip-rings, of slip power from the rotor of an asynchronous machines toa stationary machine component is known from DE 199 53 583 C1. Saidtransformer comprises a stationary primary part and a rotating secondarypart mounted on the shaft of the asynchronous machine. Each of saidparts carries an alternating-current winding with tangentially woundcoils.

An electric motor and a method for making a laminated core of a statorof an electric motor is known from DE 198 42 948 A1.

A non-contact type transformer in which each disk-shaped magnetic coreis formed by a combination of several fan-shaped cores is known from DE100 20 949 A1. Said magnetic cores each have at least one concentric andone radial slot for receiving the windings.

An electromagnetic coupler for transferring energy is known from EP 0688 028 A1. In both the primary stage and the secondary stage, the coreis annularly arranged and has annular grooves in which ring-shaped coilsare set. The core arrangement comprises at least one package withlaminated transformer elements.

A transformer for a computer tomography (CT) system is known from U.S.Pat. No. 5,608,771. Both the stator core and the rotor core are integralin construction and have at least one annular slot for receiving thewindings.

A magnetic material for power transmission cores with low permeabilityand low power loss, in the form of a homogenous composition of ferriteand plastic, is known from DE 42 14 376 A1.

BRIEF SUMMARY OF THE INVENTION

One object of the present invention is therefore to provide atransformer in which the dissipation heat is reduced, and which cantherefore have smaller dimensions, or, with the same dimensions, cantransfer a greater amount of power.

This object is achieved with a transformer pursuant to claim 1.

The invention is based on the realization that, in known rotary machinessuch as asynchronous machines, structural depth is a factor thatcontributes substantially to the heat dissipation problem. Conversely,this means that a substantial part of the heat dissipation problem canbe solved with a construction that is as thin as possible.

According to the invention, the transformer has a rotating bodycomprised of members in the shape of ring segments, wherein saidrotating body has slots that are open in the axial or radial direction,and the material of said members is ferrite. In this way, it is possibleto create a rotating body with favorable magnetic properties and withoutair gaps, and which allows power to be transferred with a particularlylow amount of loss.

In order to keep forces acting on the transformer away from the rotatingbody and hence to prevent deformation of or damage to the latter, asupport structure for receiving the members is provided.

In a wind turbine fitted with a transformer according to the invention,the excitation power can be transferred, for example, from thestationary member of the wind turbine to the rotating member, such asthe rotor of the generator. Of course, it is also possible to use aplurality of adjacent transformers for multiphase transmission.

A frequency of up to 300 kHz, preferably of about 20 kHz, has provenadvantageous for operating a transformer according to the invention suchthat the effect of inductance and the loss of energy are minimized.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantageous developments of the invention are described in thesubclaims. The invention shall now be described in detail with referenceto the drawings, which show:

FIG. 1 shows a side view of a first embodiment of a rotating body;

FIG. 2 shows a single segment of the rotating body in FIG. 1;

FIG. 3 shows a cross-sectional view along line A-A in FIG. 1;

FIG. 4 shows a side view of a second embodiment of the rotating body;

FIG. 5 shows a cross-sectional view of the second embodiment of therotating body, along line B-B in FIG. 4;

FIG. 6 shows a perspective view of the arrangement of two rotatingbodies;

FIG. 7 shows a partial cross-section of the rotating bodies;

FIG. 8 shows a partial cross-section of an alternative arrangement ofthe rotating bodies;

FIG. 9 shows a perspective view of a member for one of the rotatingbodies in FIG. 8; and

FIG. 10 shows a perspective view of a member for the other rotating bodyshown in FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a ring of a transformer 10 according to the invention. Saidring has a support structure 12 into which members 14 are inserted. Saidmembers 14 fill completely the inner space formed by the supportstructure 12, with the result that there is no air gap between theseparate members 14. A slot 16 is defined in each of the members 14. Theannular arrangement of the members 14 results in an annular slot 16 intowhich a winding can be placed.

FIG. 2 shows a single member 14 in plan view. In said view, the ringsegment shape of the member can be clearly seen. Segment 14 has an upperbar 15, a lower bar 17 and a cross-piece 19 therebetween. Bars 15, 17run substantially perpendicular to the cross-piece 19, such that aU-shaped cross-section results, wherein bars 15, 17 and the cross-piece19 define the slot therebetween.

Said U-shaped cross-section can be seen well in FIG. 3, which is across-sectional view along line A-A in FIG. 1. The support structure 12into which the member 14 is inserted is also included in said Figure,and is likewise shown here with a U-shaped cross-section. It can also beseen from said Figure that the member 14 comprising bars 15, 17 andcross-piece 19 is of integral construction. A winding 18 is placed intothe slot, and the remaining space inside the slot is filled with afilling compound 20. Said filling compound serves, on the one hand, tofixate the winding in the slot and, on the other hand, providescorrosion protection by preventing any penetration of moisture into theslot.

FIG. 4 shows an alternative embodiment of a transformer ring 10according to the invention. Here, too, members 14 are shown inside thesupport structure 12. Said members 14 are similar to those shown in FIG.1 and likewise form ring segments. Likewise, there is an annular slot 16into which a winding can be placed. In addition to the fact that each ofthe members 14 shown in the form of ring segments in FIG. 4 extendsacross a larger radian measure than shown in FIG. 1, another differenceconsists in the different structure of the members 14. This differencecan be clearly seen in FIG. 5.

FIG. 5 shows a cross-section along line B-B in FIG. 4. It can be seenfrom FIG. 5 that a U-shaped support structure 12, into which the member14 is received, is likewise provided. Said member 14 also has a U-shapedcross-section, but the upper bar 15, the lower bar 17 and thecross-piece 19 are configured as separate parts that are joined togetherto form a U-shape. This embodiment simplifies production of the bars 15,17 and the cross-piece 19. Between said bars 15, 17 and the cross-piece19, a slot is likewise formed within which a winding 18 is accommodated,said slot being filled with a filling compound 20.

FIG. 6 shows two transformer rings 10 axially opposite each other.However, it must be noted here that the gap between said transformerrings 10 in this Figure is shown with this size for illustrationpurposes only, and in normal operation is kept as small as possible. Inthis Figure, support structures 12′ and 12″ can again be seen, withinwhich members 14 form the magnetic ring inside which the winding 18 andthe filling compound 20 are installed in a slot. One of these twotransformer rings 10 is connected to a stationary portion of a device,for example the generator stator of a wind turbine, whereas the othertransformer ring 10 is connected to a rotating portion, for example therotor of a ring generator. The axis of rotation is shown by a dot-dashline. Since both transformer rings 10 are exactly opposite each other,energy can be transferred from the primary winding via the magneticcircuit to the secondary winding, as in a transformer.

This is further elucidated in FIG. 7. Said Figure shows across-sectional view through the upper portion of two oppositetransformer rings 10. Both transformer rings 10′, 10″ have a supportstructure 12′, 12″, inside which the magnetic circuit is formed bymembers 14′ 14″, shown here as integral elements. It is important herethat the gap between the opposite members, and hence the air gap in themagnetic circuit, is as small as possible, for example 0.1 mm-10 mm.Windings 18′, 18″ are disposed in each of the slots defined by members14′, 14″. Winding 18′ shown on the left in said Figure is the primarywinding, and winding 18″ shown on the right is the secondary winding. Inthe primary winding, the direction of current flow is shown pointingaway from the viewer. This causes a magnetic field, with orientation asshown by the arrows, in the magnetic circuit formed by members 14′, 14″.Said magnetic field induces a voltage in the secondary winding 18″, saidvoltage producing a flow of current towards the viewer in direction o.In this way, electrical power is transferred by this transformer fromthe primary (left) side to the secondary (right) side.

FIG. 8 likewise shows two transformer rings 10. However, these arearranged so that they face each other in a radial direction. Here, too,support structures 12′, 12″ are provided that support integral members14′, 14″ that in turn form the magnetic circuit. In said FIG. 8, thelower winding is the primary winding and the upper winding is thesecondary winding. The direction of current flow in the primary windingis again away from the viewer. A magnetic field is thus generated in themagnetic circuit, with orientation as indicated by the arrows, saidfield inducing a voltage in the secondary winding that causes a flow ofcurrent in the direction of the viewer. In this radial arrangement aswell, the gaps between the members 14′ 14″ of the magnetic circuit, andhence the air gap in the magnetic circuit, must be as small as possible,for example 1 m-3 mm.

FIG. 9 shows a member 14 in a simplified perspective view. It is evidentfrom the shape of said member 14 that a plurality of such membersarranged in sequence will result in a ring with a slot 16 that isdownwardly open. Accordingly, members 14 with this shape are installedin the upper support structure 12 in FIG. 8 and form a ring with adownwardly open slot 16.

FIG. 10 likewise shows a simplified perspective view of a member 14.Said member 14 is fitted into the lower support structure 12 in FIG. 8,thus forming a ring with an upwardly open slot.

By using the members shown in FIGS. 9 and 10, it is possible tomanufacture a transformer pursuant to the invention with rings radiallyopposite each other.

The intended use of the transformer according to the invention, forexample in operating a generator, e.g., a synchronous machine, is tofeed the electrical control power to the rotor of the generator. Saidcontrol power may be in a range in excess of 50 kW, for example, andpreferably in a range between about 80 kW and 120 kW.

The particular advantage of the transformer according to the inventionis that the slip-ring rotor used hitherto for applying electricalexcitation power to the rotor of the generator is no longer necessary,thus avoiding what was previously a source of wear and tear in the windturbine. Since the electrical excitation power is transferred wirelesslyusing the transformer according to the invention, no such wear and tearoccurs.

An electrical transformer according to the invention can be used, inparticular, in synchronous generators/ring generators. Such generatorshave a relatively large diameter at power ratings greater than 500 kW,e.g., more than 4 m, and therefore provide sufficient space toaccommodate the transformer according to the invention.

All of the above U.S. patents, U.S. patent application publications,U.S. patent applications, foreign patents, foreign patent applicationsand non-patent publications referred to in this specification and/orlisted in the Application Data Sheet, are incorporated herein byreference, in their entirety.

From the foregoing it will be appreciated that, although specificembodiments of the invention have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

1. A transformer for transferring electrical power from a stationary member to a rotating member, comprising: an annular core form for receiving an annular winding and having annular slots open in the axial or radial direction, and with an annular primary winding and an annular secondary windings disposed in the annular slots, the primary and secondary windings arranged axially or radially opposite each other, the primary winding disposed on the stationary member and the secondary winding disposed on the rotating member; and a plurality of members having a U-shaped cross-sectional configuration and of an integral construction and in the shape of ring segments that are a part of the core form.
 2. The transformer of claim 1, comprising a support structure that receives the stationary and rotating members.
 3. The transformer of claims 1, wherein the material of the stationary and rotating members is ferrite.
 4. The transformer of claim 1, wherein the stationary and rotating members are formed of toroidal tape cores.
 5. A wind turbine with at least one transformer according to claim
 1. 6. The wind turbine of claim 5, comprising a synchronous generator in which the transformer according to claim 1 is used to transfer to the rotating member of the generator excitation power necessary for operating said generator.
 7. A method for operating a transformer according to claims 1, comprising an operation frequency of up to 300 kHz.
 8. The method of claim 7 wherein the frequency of operation is 20 kHz.
 9. A generator of a wind turbine in which the transformer of claims 1 is used to transfer to the rotating member of the generator excitation power necessary for operating said generator. 